The present invention is directed to electrical power supply devices, and especially to electrical power supply devices generating power using a plurality of generating units operating in a plurality of phases.
One design parameter involved in designing a power supply apparatus is the amount of capacitance one desires or needs at the output of converters providing current to the load. Capacitance may occupy significant area in implementing circuitry, such as power supply circuitry. The amount of capacitance required is at least partially dependent upon the amount of ripple current presented by the power supply device to the load. One benefit of reducing output capacitance is that the power supply apparatus may be configured using less board space and consequently be a smaller portion of a product in which it is employed. In today's marketplace with its emphasis on smaller more compact products, such a reduction in size is beneficial.
Multiphase DC-DC power supply apparatuses, especially multiphase power supply apparatuses embodied in multiphase converter apparatuses, have evolved to deliver more current to a load that is achievable using a single phase converter apparatus. Multiphase DC-DC apparatuses contribute other attributes as well such as, by way of example and not by way of limitation, increasing frequency of output ripple current from the power supply apparatus. Such reducing of output ripple current may permit some reduction in size of output capacitance for the power supply apparatus.
However, at least some capacitance is usually necessary for a power supply apparatus because ripple currents produced by inductors in the apparatus generally remain and must be accommodated. Capacitance at the output of a power supply apparatus also permits holding output voltages in regulation between the time a step increase in the load occurs and the time the control loop of the power supply apparatus can respond to the step load increase.
There is a need for an apparatus and method for controlling provision of power to a load by a plurality of generating devices such as a multiphase power supply apparatus that can efficiently respond to a step increase in a load yet minimize capacitance required at the power supply output.